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Quantum interference effect in electron tunneling through a quantum-dot-ring spin valve.

Ma JM, Zhao J, Zhang KC, Peng YJ, Chi F - Nanoscale Res Lett (2011)

Bottom Line: It is shown that the magnitudes of these quantities are sensitive to the relative angle between the leads' magnetic moments and the quantum interference effect originated from the inter-lead coupling.We pay particular attention on the Coulomb blockade regime and find the relative current magnitudes of different magnetization angles can be reversed by tuning the inter-lead coupling strength, resulting in sign change of the TMR.For large enough inter-lead coupling strength, the current spin polarizations for parallel and antiparallel magnetic configurations will approach to unit and zero, respectively.PACS numbers:

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics, Bohai University, Jinzhou 121000, China. chifeng@semi.ac.cn.

ABSTRACT
Spin-dependent transport through a quantum-dot (QD) ring coupled to ferromagnetic leads with noncollinear magnetizations is studied theoretically. Tunneling current, current spin polarization and tunnel magnetoresistance (TMR) as functions of the bias voltage and the direct coupling strength between the two leads are analyzed by the nonequilibrium Green's function technique. It is shown that the magnitudes of these quantities are sensitive to the relative angle between the leads' magnetic moments and the quantum interference effect originated from the inter-lead coupling. We pay particular attention on the Coulomb blockade regime and find the relative current magnitudes of different magnetization angles can be reversed by tuning the inter-lead coupling strength, resulting in sign change of the TMR. For large enough inter-lead coupling strength, the current spin polarizations for parallel and antiparallel magnetic configurations will approach to unit and zero, respectively.PACS numbers:

No MeSH data available.


Schematic picture of single-dot ring with noncollinearly polarized ferromagnetic leads.
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Figure 1: Schematic picture of single-dot ring with noncollinearly polarized ferromagnetic leads.

Mentions: Up to now, the magnetic configurations of the leads coupled to the QD-ring are limited to collinear (parallel and antiparallel) one. To the best of our knowledge, transport characteristics of a QD-ring with noncollinear magnetic moments have never studied, which is the motivation of the present paper. As shown in Figure 1 we study the device of a quantum ring with a QD inserted in one of its arms. The QD is coupled to the left and the right ferromagnetic leads whose magnetic moments lie in a common plane and form an arbitrary angle with respect to each other. There is also a bridge between the two leads indicating inter-lead coupling. It should be noted that such a QD-ring connected to normal leads has already been realized in experiments[35-40]. Considering recent technological development[4-6], our model may also be realizable.


Quantum interference effect in electron tunneling through a quantum-dot-ring spin valve.

Ma JM, Zhao J, Zhang KC, Peng YJ, Chi F - Nanoscale Res Lett (2011)

Schematic picture of single-dot ring with noncollinearly polarized ferromagnetic leads.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211328&req=5

Figure 1: Schematic picture of single-dot ring with noncollinearly polarized ferromagnetic leads.
Mentions: Up to now, the magnetic configurations of the leads coupled to the QD-ring are limited to collinear (parallel and antiparallel) one. To the best of our knowledge, transport characteristics of a QD-ring with noncollinear magnetic moments have never studied, which is the motivation of the present paper. As shown in Figure 1 we study the device of a quantum ring with a QD inserted in one of its arms. The QD is coupled to the left and the right ferromagnetic leads whose magnetic moments lie in a common plane and form an arbitrary angle with respect to each other. There is also a bridge between the two leads indicating inter-lead coupling. It should be noted that such a QD-ring connected to normal leads has already been realized in experiments[35-40]. Considering recent technological development[4-6], our model may also be realizable.

Bottom Line: It is shown that the magnitudes of these quantities are sensitive to the relative angle between the leads' magnetic moments and the quantum interference effect originated from the inter-lead coupling.We pay particular attention on the Coulomb blockade regime and find the relative current magnitudes of different magnetization angles can be reversed by tuning the inter-lead coupling strength, resulting in sign change of the TMR.For large enough inter-lead coupling strength, the current spin polarizations for parallel and antiparallel magnetic configurations will approach to unit and zero, respectively.PACS numbers:

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics, Bohai University, Jinzhou 121000, China. chifeng@semi.ac.cn.

ABSTRACT
Spin-dependent transport through a quantum-dot (QD) ring coupled to ferromagnetic leads with noncollinear magnetizations is studied theoretically. Tunneling current, current spin polarization and tunnel magnetoresistance (TMR) as functions of the bias voltage and the direct coupling strength between the two leads are analyzed by the nonequilibrium Green's function technique. It is shown that the magnitudes of these quantities are sensitive to the relative angle between the leads' magnetic moments and the quantum interference effect originated from the inter-lead coupling. We pay particular attention on the Coulomb blockade regime and find the relative current magnitudes of different magnetization angles can be reversed by tuning the inter-lead coupling strength, resulting in sign change of the TMR. For large enough inter-lead coupling strength, the current spin polarizations for parallel and antiparallel magnetic configurations will approach to unit and zero, respectively.PACS numbers:

No MeSH data available.